AC self-bearing motors with a bridge configured winding

Magnetic levitation bearings eliminate friction, wear and the need for lubrication and so have high speed capability and potential for vibration control. One noteworthy development in the realm of magnetic levitation is the self-bearing or bearingless motor - an electromagnetic machine that supports its own rotor by way of magnetic forces generated by windings on its stator. Accordingly, various winding schemes have been proposed to accomplish the task of force production. This thesis proposes a novel concept of winding based on a bridge connection for polyphase self-bearing rotating electrical machines with the following advantages: • the connection uses a single set of windings and thus power loss is relatively low when compared with self-bearing motors with conventional dual set of windings. • the motor and levitation controls are segregated such that only one motor inverter is required for the normal torque production and levitation forces are produced by using auxiliary power supplies of relatively low current and voltage rating. The usual way of controlling the motor is retained. • there are many variant winding schemes to meet special needs. • independent power supplies for levitation control offer redundancy for fault tolerance. This thesis dwells specifically on the conceptual design and implementation of the proposed single set of windings scheme. The new connection has been verified to exhibit characteristics of a self-bearing motor via coupled-field finite element analysis: results are crosschecked analytically. Power loss and other aspects such as cost, design implementation are compared to support the newly proposed connection as a potential alternative to present designs.

Vertical flotation of particles in a paramagnetic fluid

Hirota et al. [6] found that the magneto-Archimedes force could be used to levitate biological materials at different heights in pressurized oxygen, providing the possibility to separate them. However the magnetic levitation of mineral particles has not been widely explored. With this in mind some preliminary experiments were performed by levitating pure mineral materials in a paramagnetic solution manganese (II) chloride. Besides the report of levitation heights of various mineral particles in manganese (II) chloride solution, the lines obtained from the basic formula provided by previous researchers were compared with experimental data. The act of cryogenic paramagnetic fluid in the magneto-Archimedes levitation was also demonstrated. The obtained results are compared with the same particle levitation heights in manganese (II) chloride solution. © 2014 Elsevier B.V.